The invention relates to an implant, in particular a vascular prosthesis which has a structured material component and a protein matrix with pore structure, and to process for its production and its use.
Many implants and processes for their production are known in the art. “Implants” generally mean devices which are inserted into a patient's body, at least temporarily, and which are intended to exert for example therapeutic, supporting or articular functions.
Implantable structures are used especially in the field of tissue engineering, an interdisciplinary research area which is concerned with processes and materials for producing artificial tissue and organ systems. Thus, for example, artificially produced implants can be used as skin, bone, cartilage, lens or vessel substitute.
Implants in the form of vascular prostheses are employed as substitute for a natural diseased vessel. The diseased section of vessel is removed and replaced by an implant. Thus, for example, small-lumen implants are employed in vascular surgery especially when the endogenous vessels of a patient cannot be used. This is the case for example when a specific length of vessel is required, or if the autologous vessels cannot be employed because of pathophysiological properties. Vascular prostheses made of synthetic material are employed here, use being made in particular of synthetic materials such as, for example, knitted or woven threads of polyethylene terephthalate (PET) or vascular prostheses made of expanded polytetrafluoroethylene (ePTFE).
Vascular implants made of these synthetic materials are preferably used because they have advantageous structural and biocompatible properties. Thus, on the one hand, surrounding tissue is able to grow in and, on the other hand, blood plasma must not escape through the pores. This is achieved through the pore size adjusted with the ePET implants, whereas knitted and woven PET implants are impregnated by coating with absorbable materials such as, for example, collagen or gelatin. Following implantation, the coating is absorbed at the rate at which the surrounding newly formed tissue grows into the porous collagen layer.
It is known that the use of the implants described above in the small-lumen vessel range leads to high rates of occlusion. This is because in particular contact of slow-flowing blood with synthetic surfaces may lead to activation of the coagulation system, the complement system and the immune system.
Further approaches to avoiding blood coagulation are in the direction of colonizing the coated implants with cells such as, for example, endothelial cells and smooth muscle cells. Interaction of the various cell types which are present for example in natural vessels, and the cell-matrix interaction are important for the functionality of the implants. Thus, besides high biocompatibility, it is also necessary to ensure that the structure of the implant is suited to the requirements of various cells.
Implants are subject to special mechanical and structural requirements. Thus, besides a sufficient structural stability, they should also have a force and stretching behaviour adapted to the tissue to be replaced. Implants must additionally have various fitting shapes, lengths and diameters. In addition, the microstructuring such as, for example, in the bioartificial vessel substitute the pore structure extending radially with cell-specific size plays an important role for the colonization with cells and for the growing tissue.